78 Buick Estate Wagon Rear End Ratio

Hoping someone might have this information handy, as I'm trying to identify the rear end in my 78 Estate Wagon. I suspect it's the standard 2.73 but want to be sure... The stampings on the axle are "2YJ P185D". I can decode that it is a Pontiac sourced rear end built during dayshift on July 4, but the 2YJ is what is stumping me. Here's a pic of the stamping:

All I can find online is a reference to RPO codes (which I will get next time I'm at the car's winter storage). Thanks in advance!